Learning to integrate multiple information sources is vital for advancing learners' digital literacy. Previous studies have found that learners' epistemic metacognitive knowledge about the nature of knowledge and knowing is related to their strategic integration performance. The purpose of this study was to understand how these relations come into play as students learn to integrate divergent information sources. To do so, we examined the contribution of scaffolds addressing the epistemic strategy of integration and epistemic metastrategic knowledge about this strategy. Participants were 99 high-achieving Arab Israeli ninth graders. All participants engaged in writing arguments based on divergent information sources. Students in the control condition received no scaffolds; students in the strategic condition received a strategic scaffold; and students in the metastrategic condition received both strategic and metastrategic scaffolds. Integration performance, epistemic metastrategic knowledge about integration, and absolutist, multiplist, and evaluativist epistemic perspectives were measured before, immediately after, and one month after the intervention. At pre-test, both epistemic metastrategic knowledge about integration and evaluativism were positive predictors of integration performance. The strategic scaffold led to a significant increase in integration performance and epistemic metastrategic knowledge. Adding the metastrategic scaffold led to greater improvement in epistemic metastrategic knowledge, but did not result in additional gains in strategic performance. An immediate decrease in absolutism occurred among all participants but was not sustained over time. A decrease in multiplism occurred only in the experimental groups and was sustained over time. The results suggest that epistemic growth can occur in both bottom-up and top-down directions.